Concentration of phosphate-bearing material



Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE JOHN W. LITTLEFORD,OF MULBERRY, FLORIDA, AND FRANCIS F, JOHNSTON, OF MOUNT PLEASANT,TENNESSEE, ASSIGNORS TO MINERALS SEPARATION NORTH AMERICAN CORPORATION,OF NEW YORK, N. Y A CORPORATION OF MLARYLANI) CON OENTRATION OFPHOSPHATE-BEARING MATERIAL No Drawing.

This invention relates to concentration of phosphate-bearing materialand is herein illustrated as applied to'what is known as Tennessee rockwhich is in finely divided condition or has been ground to suchcondition. Such rock often contains a high percentage of bone phosphateof lime, the desired element in a phosphate fertilizer raw material, butit also contains usually from 4% to 6% or more of iron and aluminumoxide, in the form of salts or other compounds which are extremelydeleterious in their action. These compounds often cause reversion ofthe phosphates from the available phosphate form to the insoluble form,which reduces the value of the fertilizer. They also bring about aphysical condition of the superphosphate made from it which tends tomake it wet and soggy and more diflicult to apply as a fertilizer. Theseundesired substances, containing iron and aluminum, add to theconsumption of acid, and they and/or their products in solutionact as adiluent to lower the effective free phosphoric'acid content of theliquor which is later used for the acidulation of further phosphate rockin the production of multiple superphosphate.

These substances also form troublesome compounds, difficult to filterout in the prep-' a-ration of tri-sodium phosphate and di-sodiumphosphate. Moreover the gelatinous precipitate formedby these substancesretains substantial quantities of phosphoric acid, removing it from thesolution, and reducing the yield of desired compounds.

According to the present invention, the amount of iron and aluminumcompounds present may be notably diminished and the phosphate-bearingmaterial at the same time concentrated so that the resulting material isricher in bone phosphate of lime. To eilect these results thephosphate-bearing material is treated with a sulphide, such as sodiumsulphide or hydrogen sulphide gas,and the sulphide-treated material isconcentrated, as by desliming or by froth-flotation, to remove theundesired minerals. Thirty-five cubic feet of hydrogen sulphide gas perton of dry phosphate-bearing material has been found to give asatisfactory treatment.

Application October 2, 1930. Serial No. 486,056.

Sometimes the best results have been obtained when the hydrogen sulphideis passed into a pulp containing added metallic salt adapted to, form aninsoluble sulphide,'such as copper sulphate.

Eat-ample I.-Dorr bowl thickener underflow from a plant treatingTennessee rock was fed to a Dorr bowl classlfier from which the overflowwent to waste and the rake discharge was fed to a minerals separationagitation flotation machine in the form of a 50% pulp, and hydrogensulphide was passed into the pulp through an air port. It was found thatthe hydrogen sulphlde could be added by passing it through 'a long tubeterminating well down 'into the pulp. After this treatment the contentsof the machine were fed to an under-current drag classifier, with theaddition of water, yielding as afinished product the rake discharge ofthe classifier. The results are shown in the following table in which B.P. L. represents bone phosphate of lime, and Fe O and A1 0 representiron and aluminum oxides, respectively, the amounts being stated inpercentages.

Egvample I I .Another lot of the same Dorr bowl thickener underflow wasfed to the Dorr bowl classifier from which the overflow went to waste,and the rake discharge was fed to the same minerals separation machine,where it was treated with hydrogen sulphide as above described. Thenwithout removing the pulp from the machine 0.3 pounds of sodium flowwent to waste and the rake discharge was delivered to the same mineralsseparation machine as a 50% pulp. The material was. treated withhydrogen sulphide as above described. The treated pulp was then placedFeed 1n an undercurrent drag classifier from which the overflow went towaste. The rake discharge was made into a pulp with further #1661! waterin the minerals separation machine and agitated with 0.2 pounds causticsoda, 0.6 pounds oleic acid and 4. pounds fuel oil, all per ton of feed,and a flotation concentrate separated. The results are shown in thefollowing table:

F010: and B. P. L.

Feed:

Plant Donthickener underfiow.- 71. 54 5.80 Rake discharge from firstdrag-classifier treatment 74. 47 4. Rake discharge from seconddrag-classifier treatment (after treatment with H18) 74. 47 3. 85Flotation concentrates 78. 24 3. 65 I It was found that if the thick.pulp was stored overnight after treatment with hydrogen sulphide, itfailed to yield equivalent results unless it had been kept well doveredwith water.

Example IV.A mixture of the coarse material known as classifier sandsand the coarse material known as cone. sands, separated in waterclassification steps from a concentration treatment of ground Tennesseephosphate rock, was reground in a mill until the material allpassed35-mesh. The contents of the mill were transferred to a mineralsseparation subaeration testing machine, using as little water aspossible. This pulp was agitated for one minute with the furtheraddition of 0.08 pounds hydro-chloric acid and 0.45 pounds of coppersulphate, both per ton of dry material. Hydrogen sulphide was thenpassed into the pulp through the air intake of the testing machine untilthe pulp was black. This required rather less than the 35*- cubic feetof I-LS gas per ton otherwise deemed advisable. Then there were added0.1 pound of Procter and Gamble soap powder and 0.5 pounds of crude pinetar oil, both per ton of dry material, the pulp diluted and agitated toproduce a preliminary or reject froth relatively rich in iron andaluminum and in insolubles, which was separated as long as any solidmaterial was carried over.

The remaining pulp was dewatered, made into a pulp with fresh water, andreagitated in the same machine with the addition of 0.5

pounds caustic soda, 0.6 pounds oleic acid, and 4.5 pounds of fuel oil,all per ton of dry feed, to 'eld a froth phosphate mat-concentrate andtailing. The concentrate thus obtained was put back into the machine andreagitated to yield a finished concentrate and a middling. The resultsare shown in the following table.

We ht B. P. L. Fe;O| and 100 71.09 use 9.29 15. 01 50. a4 9. 1 21.2081.99 1 75.17 4.1 8.47 58.13 78.78 s 5.00 8.93 74.66 4.35 8.48 11. 4363. 34 5. 71 21. 4o

It will be noted from this table that the final reject or tailingcontains substantially more of the iron and aluminum compounds than doesthe mat phosphate-bearing concentrate. Thus it appears that thetreatment with hydrogen sulphide in the presence of the copper sulphateresulted not only in making a substantial part of the iron and aluminumcompounds morefioatable than the phosphate material, but also resultedin making another substantial part of the iron and aluminum compoundsless floatable than the desired phosphate material. In this way iron andaluminum compounds of two types were removed, one type in a froth andanother type in the final tailing.

Exmmple V.Another lot of the same material was subjected tosubstantially the same treatment and produced a slightly richer floatand a smaller recovery, with a slight altering of theconditions of thefinished concentrate carrying 79.87% B. P. L, equal to 43.7% of thecrude material.

Other tests on slightly difierent lots of phosphate material gaveparallel results. It was found that a solution of sodium oleate gavesubstantially the same results as the soap powder. Doubling the amountof copper sulphate gave a rather better result in the treatment of lowergrade feed.

Having thus described certain embodiments of the invention, what isclaimed is:

1. The process of concentrating a phosphate-bearing material whichconsists in agitating a pulp of the material so as to mix it with asulphide, and separating iron-andaluminum-containing compounds from thebulk of the phosphate-bearing material.

2. A process of concentrating phosphatebearing material which consistsin agitating a thick pulp of the material containing hydrogen sulphideand thereafter separating ironand-aluminum-containing compounds from therest of the material.

7 3. A process of concentrating phosphatebearing material which consistsin agitating a thick pulp of ,the material while passing hydrogensulphide into it, and theretained in the phosphate-bearing material.

5. A process of concentrating phosphatebearing material which consists nagitatlng a pulp of the material with hydrogen sulphide, separatingiron-and-aluminum-containing compounds from the rest of the material,and then subjecting the pulp to a flotation operation to produce aphosphate-bearing mat concentrate, and separating the concentrate.

6. A process of concentrating phosphatebearing material which consistsin agitating a thick pulp of the material with a sulphide, thinning thepulp separating iron-and-aluminum-containing compounds from the pulp bya froth-flotation operation, and thereafter concentrating the remainderof the pulp by flotation to yield a phosphate-bearing float concentrate,and separating the concentrate;

7. A process of concentrating phosphatebearing material which consistsin agitating a pulp of the material with a metallic salt adapted toyield an insoluble sulphide, agitating with a soluble sulphide," toprecipitate I the metallic sulphide, and separating iron and aluminacompounds from'the bulk of the phosphate-bearing material. l-

8. A\ process of concentrating phosphatebearing material which consistsin agitating a pulp of the material with a metallic salt adapted toyield an insoluble sulphide, agitating with hydrogen sulphide toprecipitate the metallic sulphide, separating iron and alumna compoundsfrom the remainder of the phosphate-bearing material, and contentratingsaid remainder.

9. A process of concentrating phosphatebearing material which consistsin agitating a thick pulp of the material with copper tating a pulp ofthe remainder to yield a phosphate-bearing concentrate.

11. A process of concentrating phosphatebearing material which consistsin agitating a pulp of the material with copper sulphate and added acid,further agitating the pulp with hydrogensulphide to precipitate coppersulphide, separating. iron and alumina compounds from the remainder ofthe phosphatebearing material by agitating the thin pulp of the materialwith a flotation agent to form an iron-and-alumininn-bearing froth,separating the froth, dewatering the pulp, agitating the thinned pulpwith other flotation agents to yield a floating phosphate-bearing floatconcentrate, and separating the float.

In testimony whereof, we have signed this specification.

JOHN W. LITTLEFORD. FRANCIS F. JOHNSTON.

sulphate and'with a soluble sulphide so that copper sulphide isprecipitated, separating iron and alumina compounds from the remainderof the phosphate-bearing material by froth flotation, and concentratingsaid mainder.

10. A process of concentrating phosphata I bearing material whichconsists in agitating pulp of the material with copper sulphate and withhydrogen sulphide so that copper sulphide is precipitated, separatingiron and alumina compounds from the remainder of the"'phosphate-bearingmaterial by froth flo- I tation, dewatering said remainder, and agi-CERTIFICATE OF CORRECTION.

Patent No. l, 838,422."- W i December 29. 1931.

JOHN ii. Llmurouuqm AL.

It is hereby certif that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 1, line82, for the last figure in the boiced'table ".45" read 3.45; and thatthe said Letters Patent should be read with this correction therein thatthe same may conform to th record f the use in the Patent Office Signedand sealed this 17th daiof September, A D. 1935.

Leslie Frazer (Seal) Acting Commissioned Patents.

